According to a new Greenpeace report, the levels of harmful air particles in areas around Beijing have dropped by 25 percent in the past two years. That's noteworthy because most of the country's coal production happens there.

In surveyed cities across the country, annual average levels of harmful particulate matter in the air dropped by more than 10 percent in 2015.

But despite the improvement, China still has a lot of work to do before it can match the World Health Organization's air quality standards.

A Greenpeace campaigner told NBC: "None of these 366 cities meet the World Health Organization's air quality standard. That is to say, 100 percent of Chinese cities studied fail to meet the WHO's standard."